The present invention relates to an apparatus and method for compacting or compressing a material in a mold. More particularly, the present invention relates to an apparatus and method which simulates actual road building conditions for compacting an asphalt and aggregate mixture in a mold to form an asphalt and aggregate slab having a substantially uniform thickness and density.
The present invention is designed to form asphalt and aggregate slabs for testing purposes. These slabs are tested on wheel tracking machines or other test equipment to test the strength and durability of a particular asphalt and aggregate mixture. In addition, test specimens of other shapes can be cut from these slabs. These test specimens can then be tested on other test equipment. By testing various combinations of asphalt and aggregate, it is possible to select a mixture that will be more durable and last longer when the mixture is applied to a road.
Asphalt roads are formed by placing a layer of asphalt and aggregate mixture over the road surface to be covered. This mixture is then compacted with a roller. The roller compresses the mixture to a predetermined density and aligns the aggregate pieces in the mixture without breaking the aggregate. The compacted asphalt and aggregate mixture has a substantially uniform thickness and density.
It is desirable to produce asphalt and aggregate slabs for testing purposes which simulate the mixture after it has been applied to the road. In a previous method of forming asphalt slabs for testing, the asphalt and aggregate mixture is tamped or pounded in a mold to compress the mixture. However, the impact can crack or break the aggregate stones in the mixture. This results in a sample that is different than the actual road constructed with that mixture. Therefore, this previous pounding method does not simulate actual road mixture of asphalt and aggregate.
In another previous method of forming asphalt slabs for testing, the asphalt and aggregate mixture is compressed in a mold using a roller or wheel applied directly on the surface of the mixture. Using rollers typically avoids the problem of cracking and breaking the aggregate stones. However, the mixture compressed with the roller tends to well up in front of and behind the roller at each end of the mold making it difficult or impossible to form slabs having a uniform thickness and density. Therefore, the direct contact roller method is also ineffective for producing test slabs which simulate an actual road surface.
The present invention makes it possible to make asphalt slabs having a substantially uniform thickness and density in which the aggregate in the mixture is aligned and not cracked or broken. In other words, the present invention produces slabs substantially identical to slabs cut from an actual road surface.
According to one aspect of the present invention, an apparatus is provided for compressing a material in a mold. The apparatus includes a frame having a first portion and a second portion. The apparatus also includes means coupled to the first portion of the frame for compressing the material in the mold, and a support plate coupled to the second portion of the frame for receiving the mold thereon to position the mold relative to the compressing means. The apparatus further includes means for varying the distance between the compressing means and the support plate so that the compressing means applies a compressive force to the material, and drive means coupled to the support plate for moving the support plate relative to the compressing means in a direction normal to the compressive force applied by the compressing means.
Illustratively, the compressing means is a roller coupled to the first portion of the frame for applying a compressive force to the mold. It is understood that the drive means can be any means which provides relative movement between the compressing means and the support plate in a direction normal to the direction of the compressive force.
According to another aspect of the present invention, an apparatus is provided which includes a frame, a mold for receiving the material therein, and means for supporting the mold on the frame. A plurality of plates are inserted into the mold in a side by side relationship with an edge of each plate in contact with the material. The apparatus also includes means coupled to the frame for applying a compressive force against the plurality of plates in the mold to compress the material.
According to yet another aspect of the present invention, a method is provided for compressing a material. The method includes the steps of placing the material in a mold, placing a plurality of plates in the mold in a side by side relationship over the material with an edge of each plate in contact with the material so that said plates substantially cover the material, and applying pressure against the plates so that the plates compress the material located in the mold. The method also includes the step of adjusting the distance between the mold and the pressure applying means as the material is compressed, and the step of providing relative movement between the mold and the pressure applying means in a direction normal to a compression force applied by the pressure applying means.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.